1. Field of the Invention
The present invention is directed to a shock wave source of the type suitable for treating calculi in the body of a patient by disintegrating the calculi.
2. Description of the Prior Art
Shock wave sources are known for use in lithotripsy which include a liquid-filled shock wave tube having one end closed by a flexible cover which can be pressed against the patient by means of the fluid pressure of the liquid, and an opposite end which is closed by a membrane. The membrane is disposed opposite a flat coil with an insulating layer therebetween. The coil is connected to a high voltage pulse generator.
Shock wave sources of this type are used, for example, for disintegrating kidney stones. For this purpose, an acoustic lens is disposed in the shock wave tube, which focusses the shock wave generated by the flat coil and the membrane to a focus at which the kidney stone is disposed. The particles of the kidney stone disintegrated in this manner can then be eliminated naturally.
In known shock wave sources, the flat coil is formed by a helical winding, having one end which is grounded. The membrane disposed opposite the coil consists of electrically conductive material, and is also grounded. When a high voltage pulse is supplied to the flat coil, the membrane is magnetically repelled due to the eddy currents produced, and initially generates a planar shock wave in the fluid in the shock wave tube, which is focussed onto the calculus by the acoustic lens. The voltage between the coil at its high-voltage end and the membrane is the same as the maximum value available from the high-voltage source, so that arcing, which can destroy the membrane, may occur.